The present invention relates to an electron gun for a cathode ray tube, and more particularly, to a cathode structure in which a combining structure of an electron emission array cell and a supporter for supporting the same is improved, and an electron gun for a cathode ray tube using the cathode structure.
A typical cathode ray tube, as shown in FIG. 1, includes a panel 10 on which a fluorescent film is formed, a funnel 20 sealed with the panel 10, an electron gun 30 installed at a neck portion 21 of the funnel 20, and a deflecting yoke 23 installed at a cone portion 22 of the funnel 20. In the cathode ray tube structured as above, an electron beam emitted from the electron gun 30 is deflected by the deflecting yoke 23 and scanned onto the fluorescent film 11 to form an image by exciting the fluorescent film 11.
FIG. 2 shows an example of an electron gun for emitting thermions which is installed at the neck portion 21 of the funnel 20.
The electron gun is comprised of a cathode structure 31 comprised of three electrodes, a control electrode 32 and a screen electrode 33, a focus electrode 34 and a last accelerating electrode 35 which are sequentially installed from the screen electrode 33.
In the electron gun 30 configured as above, when a predetermined voltage is applied to the cathode structure 31 and the respective electrodes (32-35), thermions are emitted from the cathode structure 31 and simultaneously electron lenses are formed between the respective electrodes 32-35. Thus, the electron beam emitted from the cathode structure 31 is focused and accelerated as passing through the electron lenses formed between the respective electrodes.
In such an electron gun, a significant amount of the time required to emit the electron beam at a normal beam current density is taken up by the cathode structure. Thus, the cathode structure as a source for emitting electrons serves as an important factor in the electron gun.
The cathode structure is largely classified into an indirectly heated cathode in which thermions are emitted by heating electron-emitting material and a cold cathode in which electrons are emitted using an electrical field. In FIG. 3, an example of the cathode structure using a field emission array cell which is of the cold cathode type is illustrated.
As illustrated in the drawing, a cathode structure 40 includes a rimmed electrode member 41, an insulating member 42 inserted into the electrode member 41, a field emission array cell 44 disposed atop the insulating member 42, and pins 45 located at the insulating member 42 to supply power to the field emission array cell 44.
However, in the above-mentioned cathode structure 40, since a base member 44a of the field emission array cell 44 is attached to the upper surface of the insulating member 42, the field emission array cell 44 can be easily detached from the insulating member 42. That is, when the electron gun is heated at high temperature during a sealing or gas-exhausting step in a process of manufacturing the cathode ray tube, the strength of the attachment between the insulating member 42 and the base member 44a deteriorates due to the difference in the thermal expansion coefficients of the insulating member 42 and the base member 44a. Such deterioration of the attachment lessens the strength of attachment or vibration-proof property of the insulating member 42 and the base member 44a such that either member can be easily detached from the other by a small impact or vibrations.